In humans, periods of sleep invariably follow periods of wakefulness according to a circadian rhythm (day/night alternation), partly dictated by our internal clock but also influenced by environmental stimuli (light, noise, nutrition, exercise …). But what is the impact of sleep on athletic performance?
The “why” of sleep is still poorly explained from a scientific point of view. What is clear, however, is that it contributes to the regeneration of both physical and mental capacities. This is why quality sleep is essential to effectively recover from the various activities carried out during the day (work, home, training…). Moreover, the duration and “depth” of sleep are naturally proportional to the fatigue accumulated during wakefulness. In the end, we spend nearly a third of our lives asleep.
A bit of physiology
Nighttime sleep is structured in 3 to 5 cycles of about 90 minutes each, during which the following phases alternate:
- Light slow-wave sleep, corresponding to the falling asleep phase
- Deep slow-wave sleep, accompanied by a slowdown of metabolism and a decrease in muscle tone
- REM sleep, where brain activity is intense and muscle tone is absent. This phase is conducive to dreams and is marked by rapid eye movements under closed eyelids
Falling asleep is a complex phenomenon influenced by many factors: diet, alcohol or coffee consumption, light, noise, but also circadian rhythms and homeostatic processes (adenosine secretion).
Why evening exercise can make falling asleep harder
Many people struggle with falling asleep and/or suffer from poor sleep quality. To fall asleep easily, the body needs to be in a balanced state, particularly thermally, with the body temperature close to 37°C (98.6°F).
However, most sports raise body temperature and trigger adrenaline release. At 38–39°C (100–102°F), it takes no less than 2 to 3 hours to return to 37°C. This explains why evening physical activity can cause insomnia.
It is therefore advisable to avoid intense training sessions in the evening. Physically or mentally stimulating sports are not recommended:
- Combat sports
- Squash
- Fitness
… especially if practiced indoors in an overheated environment.
The latest recommended time for training is around 7 p.m.… During the day, on the other hand, exercise can actually make it easier to fall asleep and improve sleep quality, thanks to increased energy expenditure and stress relief.
Specificities in athletes
For athletes, both the quantity and quality of sleep are essential for neural and physical recovery. It is during sleep that growth hormone secretion and glycogen replenishment are at their peak.
“Sleep is the most advanced form of rest, and therefore indispensable for athletes to optimize recovery.”
Sleep deprivation: metabolic effects and risks
Sleep deprivation directly affects metabolism. Any lack of sleep increases appetite by upregulating certain hormones (leptin, ghrelin, orexin). The result: higher energy intake, lower energy expenditure, and possible weight gain.
Sleep deprivation also disrupts the circadian rhythm of cortisol and growth hormone, both involved in blood glucose regulation, which is crucial for endurance athletes.
Links between sleep and immunity are increasingly clear: the production of certain immune mediators follows a circadian rhythm.
Finally, sleep deprivation leads to:
- Poorer thermoregulation
- Higher risk of muscle injury
In short, it’s best to get good sleep before a competition!
Sleep disorders in the general population
One in three people suffers from one or more sleep disorders. Among the most common:
- Chronic insomnia (16% of the population)
- Sleep apnea (5% of adults)
- Restless legs syndrome (8% of the population)
- Narcolepsy (0.026% of the population)
How can endurance athletes improve their sleep?
- Shower: A cool shower (20–22°C) helps lower body temperature and promotes falling asleep. Sauna and steam baths, on the other hand, maintain heat elevation and disrupt sleep.
- Relaxation: Reducing muscle tone and heart rate makes sleep easier. Stretching, meditation, or just 10 minutes of abdominal breathing can sometimes be enough to fall asleep.
- Nutrition: Caffeine, certain proteins (red meat, eggs), and heavy meals disrupt sleep in the evening. In contrast, light meals, carbohydrates (potatoes, pasta, rice…), cherries, kiwis, calming herbal teas (lime blossom, valerian), and supplements (magnesium, B12) promote falling asleep.
Focus on melatonin
Melatonin, also known as the sleep hormone, is produced in darkness by the pineal gland. In the presence of light, its production is inhibited. Released at the beginning of the night, it promotes sleep. With age, its production decreases, which explains certain sleep disorders.
Conclusion
In the age of the Internet, where our nervous system is constantly stimulated (social media, video games …), it is essential for athletes to optimize their sleep. Just like nutrition and training, sleep is a true pillar of performance and health.
References
- Inserm dossier on sleep
- Chenaoui et al., How does sleep help recovery from exercise-induced muscle injuries? J Sci Med Sport, 2021
- Keramidas ME et al., Short-term sleep deprivation and human thermoregulatory function during thermal challenges. Exp Physiol, 2021;106(5):1139-1148
- Doherty R et al., Sleep and Nutrition Interactions: Implications for Athletes. Nutrients, 2019;11(4):822
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